Results of radioiodinated very low density lipoprotein (VLDL) and high density lipoprotein (HDL) metabolic studies in man, performed in our branch over the past six years, have recently been published and reviewed. Turnover studies utilizing radiolabeled HDL, apoA-I, and apoA-II have now been completed in 12 normals, 3 Tangier homozygotes, 3 Tangier heterozygotes, 2 patients with Type I hyperlipoproteinemia and 2 patients with abetalipoproteinemia. These studies have helped to elucidate the factors regulating apoA-I and apoA-II metabolism in normal and dyslipoproteinemic subjects. Chylomicron apolipoprotein plasma kinetics have been studied in 3 normal subjects, 2 patients with hyperchylomicronemia, and 2 Tangier homozygotes. Recently, we have investigated (3H) vitamin A kinetics in 7 normal and 8 dyslipoproteinemic subjects. Vitamin A serves as a marker of chylomicron remnant metabolism. In addition, computer analysis on our patient population has been used to discern the dietary and drug factors regulating HDL cholesterol.